High flow polyolefin composition with high stiffness and puncture resistance

Abstract

The present invention relates to a polyolefin composition comprising two heterophasic propylene copolymers which differ in the intrinsic viscosity of their xylene soluble fractions, the heterophasic propylene copolymer mit with the lower intrinsic viscosity is present up to 10 wt.-% in the polyolefin composition.

1 - 16 . (canceled) 
     
     
         17 . A polyolefin composition comprising
 (a) a first heterophasic propylene copolymer (HECO1) having
 (i) a melt flow rate MFR 2  (230° C.) measured according to ISO 1133 in the range of 40.0 to 60.0 g/10 min, and 
 (ii) a xylene cold soluble content (XCS) determined according ISO 16152 (25° C.) of at least 15 wt.-%, 
   wherein further
 (iii) the intrinsic viscosity (IV) determined according to DIN ISO 1628/1 (in decalin at 135° C.) of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO1) is in the range of 2.5 to 4.3 dl/g, and 
   (b) a second heterophasic propylene copolymer (HECO2) comprising a propylene homopolymer (H-PP2) and an elastomeric propylene copolymer (E2), wherein
 (i) said second heterophasic propylene copolymer (HECO2) has a melt flow rate MFR 2  (230° C.) measured according to ISO 1133 in the range of above 1.0 to 8.0 g/10 min; 
 (ii) the xylene cold soluble (XCS) fraction of the second heterophasic propylene copolymer (HECO2) has an intrinsic viscosity determined according to DIN ISO 1628/1 (in decalin at 135° C.) in the range of more than 3.7 to 9.0 dl/g; and 
 (iii) the comonomer content of the xylene cold soluble (XCS) fraction of the second heterophasic propylene copolymer (HECO2) is in the range of 10.0 to 40.0 wt.-%, 
   wherein
 the weight ratio of the first heterophasic propylene copolymer (HECO1) and the second heterophasic propylene copolymer (HECO2) [(HECO1)/(HECO2)] is in the range of 9:1 to 200:1; and/or 
 the amount of the second heterophasic propylene copolymer (HECO2) in the polyolefin composition is equal or below 10 wt.-%, based on the total weight of the polyolefin composition. 
   
     
     
         18 . The polyolefin composition according to  claim 17 , wherein the polyolefin composition has a melt flow rate MFR 2  (230° C.) measured according to ISO 1133 of at least 40 g/10 min. 
     
     
         19 . The polyolefin composition according to  claim 17 , wherein
 (a) the second heterophasic propylene copolymer (HECO2) has a xylene cold soluble content (XCS) determined according ISO 16152 (25° C.) of below 40 wt.-%,   
       and/or
 (b) the propylene homopolymer (H-PP2) of the second heterophasic propylene copolymer (HECO2) has a melt flow rate MFR 2  (230° C.) measured according to ISO 1133 in the range of above 15 to 400 g/10 min. 
 
     
     
         20 . The polyolefin composition according to  claim 17 , wherein the second heterophasic propylene copolymer (HECO2) fulfills the in-equation (IV) 
       
         
           
             
               
                 
                   
                     0.50 
                     ≥ 
                     
                       
                         ( 
                         
                           0.241 
                           × 
                           
                             C 
                             
                               wt 
                               . 
                               
                                 - 
                                 % 
                               
                             
                           
                         
                         ) 
                       
                       - 
                       
                         ( 
                         
                           1.14 
                           × 
                           
                             IV 
                             
                               dl 
                                
                               
                                 / 
                               
                                
                               g 
                             
                           
                         
                         ) 
                       
                     
                   
                 
                 
                   
                     ( 
                     IV 
                     ) 
                   
                 
               
             
           
         
         wherein
 C is the comonomer content in wt.-% of the xylene cold soluble (XCS) fraction of the second heterophasic propylene copolymer (HECO2), and 
 IV is the intrinsic viscosity in dl/g of the xylene cold soluble (XCS) fraction of the second heterophasic propylene copolymer (HECO2). 
 
       
     
     
         21 . The polyolefin composition according to  claim 17 , wherein
 (i) the first heterophasic propylene copolymer (HECO1) has a comonomer content in the range of 6.0 to 17.0 wt.-%, and/or   (ii) the comonomer content of the xylene cold soluble (XCS) fraction of the first heterophasic propylene copolymer (HECO1) is at least 26 wt.-%.   
     
     
         22 . The polyolefin composition according to  claim 17 , wherein the second heterophasic propylene copolymer (HECO2) has a comonomer content below 20.0 wt.-%. 
     
     
         23 . The polyolefin composition according to  claim 17 , wherein the first heterophasic propylene copolymer (HECO1) comprises a polypropylene (PP1) as matrix and an elastomeric propylene copolymer (E1) dispersed in said matrix. 
     
     
         24 . The polyolefin composition according to  claim 17 , wherein the polyolefin composition comprises additionally up to 2.0 wt.-% of a nucleating agent, based on the total weight of the polyolefin composition. 
     
     
         25 . The polyolefin composition according to  claim 17 , wherein the polyolefin composition comprises
 (a) at least 85 wt.-%, based on the total weight of the polyolefin composition, of the first heterophasic propylene copolymer (HECO1);   (b) 0.5 to 10 wt.-%, based on the total weight of the polyolefin composition, of the second heterophasic propylene copolymer (HECO2);   (c) optionally up to 2.0 wt.-%, based on the total weight of the polyolefin composition, of a nucleating agent.   
     
     
         26 . The polyolefin composition according to  claim 17 , wherein the polyolefin composition has
 (a) a tensile modulus measured according to ISO 572-2 of at least 1,310 MPa, and/or   (b) a Charpy notched impact measured according to ISO 179 2C/DIN 53453 (−20° C.) of at least 4.0 kJ/m 2 , and/or a Charpy notched impact measured according to ISO 179 2C/DIN 53453 (23° C.) of at least 9.0 kJ/m 2 ; and/or   (c) a puncture energy (23° C.) measured according to ISO 6603-2 of at least 10.0 J.   
     
     
         27 . A packaging material comprising at least to 60 wt.-% of the polyolefin composition according to  claim 17 . 
     
     
         28 . The packaging material according to  claim 27 , wherein the packaging material is a thin wall packaging material having a thickness of equal or below 2 mm. 
     
     
         29 . A method of improving puncture resistance of a polyolefin composition comprising utilizing a second heterophasic propylene copolymer (HECO2) in the preparation of the polyolefin composition, wherein the amount of the second heterophasic propylene copolymer (HECO2) in the polyolefin composition is equal or below 10 wt.-%, based on the total weight of the polyolefin composition,
 wherein further the second heterophasic propylene copolymer (HECO2) comprises a propylene homopolymer (H-PP2) and an elastomeric propylene copolymer (E2),
 (i) said second heterophasic propylene copolymer (HECO2) has a melt flow rate MFR 2  (230° C.) measured according to ISO 1133 in the range of above 1.0 to 8.0 g/10 min; 
 (ii) the xylene cold soluble (XCS) fraction of the second heterophasic propylene copolymer (HECO2) has an intrinsic viscosity determined according to DIN ISO 1628/1 (in decalin at 135° C.) in the range of more than 3.7 to 9.0 dl/g; and 
 (iii) the comonomer content of the xylene cold soluble (XCS) fraction of the second heterophasic propylene copolymer (HECO2) is in the range of 10.0 to 40.0 wt.-%, 
   wherein the improvement of puncture resistance is achieved if the low temperature puncture energy at −20° C. is at least 1.8 J higher for the polyolefin composition comprising the second heterophasic propylene copolymer (HECO2) compared to the same polyolefin composition but without the second heterophasic propylene copolymer (HECO2).   
     
     
         30 . The method according to  claim 29 , wherein the polyolefin composition comprises
 (a) at least 85 wt.-%, based on the total weight of the polyolefin composition, of the first heterophasic propylene copolymer (HECO1);   (b) 0.5 to 10 wt.-%, based on the total weight of the polyolefin composition, of the second heterophasic propylene copolymer (HECO2); and   (c) optionally up to 2 wt.-%, based on the total weight of the polyolefin composition, of a nucleating agent.